Microbiological Studies on the Humification Process (Part 2) on the Aerobic Decomposition of the Fresh Plant Residue in the Case of Single Inoculation

The humification of several constituents of plant was studied by Trussow¹⁾ and Waksmans²⁾ in the Past, or by Kononova,³⁾ Tepper⁴⁾ and Laatsch⁵⁾ in recent years. In the previous paper, we experimented the microbial action on humus separated from an uncultivated soil, and showed that the inoculation of Trichoderma koningi and soil extract prqmoted the humification of the sample, but such tendency was not revealed in the case of single inocolation of two strains of Actinomyces and four strains of aerobic bacteria, and that when the humification of the soil humus was promoted it occurred, in the first place, as the transformation of the fulvic acid fraction, not as that of the precipitation part (the humic acid fraction). Following the previous report, we studied the humification process of fresh plant residue (upland rice straw) by a similar procedure.     

Some features of stelar tissues isolated from corn roots

In relation to radial ion transport to xylem vessels in higher plant roots, some features of stele, cortex, and root tip freshly isolated from 2-day-old corn roots grown under moistened or submerged condition were investigated. The contents of P, K, and Mg in primary roots decreased gradually from the apical to the basa1 region axially. The stele contained P, Na, Cu, Fe, and Mn in higher level than the cortex. The O₂ uptake rate of root tip was much higher and that of freshly isolated stele was as high as that of fresh cortex. In stele, more CN sensitive respiration was observed than in cortex. Although isolated stele absorbed tess ³²p than cortex and root tip, the incorporation of ³²p into organic compounds in stele was as much as in root tip. These results show that the freshly isolated stele has high metabolic activity and must play an inherent role in radial and selective ion transport in situ.     

Diurnal variation of tryptic activity in larval stage and development of proteolytic enzyme activities of malabar grouper (Epinephelus malabaricus) after hatching

Diurnal variation in tryptic activity and developmental changes in proteolytic enzyme activities of malabar grouper larvae (Epinephelus malabaricus) were examined. Five different groups were prepared for the experiment of diurnal variation of tryptic activity in larvae: larvae were fed Thai-type rotifers Brachionus rotundiformis from the time of mouth opening, fed rotifers from 6 h after mouth opening, 12 h, 24 h and not fed rotifers (starved control). The experimental tanks were placed in temperature-controlled baths at 28 °C under 24 h light. Developmental changes in proteolytic activity of trypsin and pepsin-like enzyme were measured from hatching to 57 days after hatching (DAH).

The tryptic activity of all fed groups showed the same pattern, and the diurnal variation of tryptic activity was clearly observed from 3 to 6 DAH. The highest tryptic activities were found at 19:00, and the activities were lowest from 01:00 to 07:00. In contrast, that of non-fed larvae was low compared to the fed groups, however the diurnal variation of tryptic activity was shown same tendency to the fed groups. Interestingly, both groups (fed and non-fed) were exhibited a circadian rhythm under the 24 h light conditions and delaying of first-feeding. Tryptic activity of larvae notably increased from 40 to 45 DAH and markedly decreased at 52 DAH. In contrast to the tryptic activity, that of pepsin-like enzyme clearly increased from 47 to 51 DAH. The results suggest that a functional change of protein digestion occurs from 40 to 50 DAH related with metamorphosis in malabar grouper. These results could contribute to determining appropriate feeding schedules, such as feeding time, frequency and optimal time to change food items, in mass-scale production of the present species.     

Depletion of naturally recruited wild Japanese eels in Okayama,Japan, revealed by otolith stable isotope ratios and abundance indices

To investigate the population dynamics of naturally recruited wild Japanese eels, fisheries data of wild individuals in Okayama Prefecture were investigated as a case study. Wild and stocked eels were discriminated using a recently developed method based on otolith stable isotopes. Of the 161 eels captured in freshwater areas where eels had been stocked, 98.1% were discriminated as stocked. In contrast, 82.8% of 128 eels captured in coastal areas where eels are not stocked were discriminated as wild. There was a significant decrease in longline and set-net catch per unit effort between 2003 and 2016 in the coastal areas where most eels were discriminated as wild, indicating ongoing depletion of wild Japanese eels in these waters.     

Characterization of Campylobacter jejuni in large-billed crows (Corvus macrorhynchos) in Tochigi prefecture,Japan

As free-living crows are a potential source of Campylobacter infections in broilers and cattle, we characterized Campylobacter spp. isolated from crows using multilocus sequence typing and antimicrobial susceptibility testing. We obtained 82 samples from 27 birds captured at seven different times using a trap set in Tochigi prefecture, Japan. Campylobacter jejuni was isolated from 55 (67.1%) of the 82 samples and classified into 29 sequence types, of which 21 were novel. Tetracycline and streptomycin resistance rates were 18.2% and 3.6%, respectively. These results show that most types of C. jejuni infecting crows differ from those isolated from humans, broilers, and cattle. Thus, the importance of free-living crows as reservoirs of Campylobacter infections in broilers and cattle may be limited.